Rotary solid dielectric variable condenser



April 28, 1964 J. E. HOWELL 3,131,338

ROTARY soun DIELECTRIC VARIABLE CONDENSER Filed April 8. 1960 FIG.2.

JAMES E. HOWELL.

IN VEN TOR.

United States Patent ()fiiice 3,131,338 Patented Apr. 28, 1964 3,131,338RGTARY SQLED DIELECTREQ VARIABLE CONDENSER James E. Howell, Huntsvilie,Ala, assignor to the United States of America as represented by theSecretary of the Army Filed Apr. 8, 1960, Ser. No. 21,065 6 Claims. (Cl.317-253) (Granted under Title 35, US. Code (1952), sec. 266) Theinvention described herein may be manufactured and used by or for theGovernment for governmental purposes without the payment of any royaltythereon.

The present invention relates to a solid dielectric variable condenserwherein fluids such as air, moisture, etc., are excluded from theinterior of the condenser. The exclusion of fluids from the electricfield of a condenser is of importance where conditions are such thationization of a fluid within the condenser may occur. This ionization offluid in a condenser takes place much more readily when the potentialacross the condenser is relatively high, or when the fluid pressure anddensity is low, e.g., at high altitudes. Both of these conditions arepresent in guided missile operations where high power requirements withcorresponding high voltages are necessary in missiles traveling at highaltitudes. In such applications a condenser must be free of all externalfluids and it also must be variable to facilitate minor adjustments.

It is therefore, an object of the present invention to provide acondenser which fulfills all of these requirements and fully overcomesthe noted problem of ionization within the? condenser.

It is a further object of this invention to provide a solid dielectricvariable condenser which excludes all fluids from its electric field.

A still further object of this invention is to provide a simple,inexpensive and practical condenser which is selectively variable andwhich will be eifective when atmospheric pressures and density is lowand voltages are high.

Other objects and advantages of this invention will become apparent uponconsideration of the following detailed description which when taken inconjunction with the accompanying drawings in which:

FIGURE 1 is a plan view of an embodiment of this invention partiallybroken away to show the circular shape of the condenser.

FIGURE 2 is a view along line 22 of FIGURE 1.

FIGURE 3 is a view. similar to FIGURE 2 but showing the variable sectionof the condenser rotated 180.

FIGURE 4 is an exploded view of the interior elements of the condenser.

As shown in FIGURE 1, a condenser 12 having a circular shape is inclosedby a non-conductive low dielectric housing 14. However, in actualpractice this nonconductive, low dielectric housing 14 may, if desired,be made an integral part of the structure or apparatus in which thecondenser is utilized. In any event, the housing provides a convenientmeans for holding the interior elements of the condenser together and toelectrically isolate the interior parts as will presently appear.Conductors 16 are used to supply potential to the electricallyconductive members of the condenser and a screw means 17 affordsadjustment of the condenser as will presently appear.

As shown in FIGURE 2, the metal cylindrical members 18 and 24 areopposing plates of the condenser 12. Voltage is applied to the cylinders18 and 26 by means of corresponding conductors 16. As shown in FIGURES1, 2 and 3, conductors 16 are secured in housing 14 and disposed incontact with cylinders 18 and 20 to supply potential thereto. Thecylinders 18 and 20 are separated by a cylindrical member 22 ofdielectric material of varying thickness and a member 32 of lowdielectric insulating material. The cylinders 18 and 20 are mounted forrelative rotation and each cylinder is provided with areas in appositionmovable in and out of registry across the dielectric member 22 forcontrol of the capacitance.

In accordance with the teachings of the present invention the dielectricmember 22 must be of varying thickness; however, this variance need notconform to the embodiment illustrated since any geometric variance ofthe lower surface 24 (FIGURE 4) of the dielectric member 22 will beoperative so long as the upper surface 26 of dielectric member 22 isflush with the outer surface 28 of cylinder 18 and the outer surface 30of insulating member 32. The upper surface 34 of cylinder 20 is soformed as to closely conform to and mate with the variance of the lowersurface 24 on dielectric member 22.

As shown in the embodiment illustrated, the electrically conductivecylindrical member 18 is mounted for r0 tation about its longitudinalaxis in housing 14 and has a single stepped portion cut into its outersurface thereby forming a cylindrical member having a single steppedsegment 35 projecting therefrom to provide a pair of outer parallelsurfaces 36 and 38 thereon. This segmental projection may, if desired,be semi-circular in shape as shown.

The segmental insulating member 32 has an inner surface 40 as well asthe outer surface 30 and is mounted to be carried by cylinder 18 forrotation therewith. The inner surface 40 is placed adjacent the outersurface 38 of cylinder 18. The outer surface 30 of member 32 then liesflush and in a plane with the outer surface 36 of cylinder 18 (FIGURES 2and 3). This insulating member 32 may, if desired, be semi-circular butthis shape may be varied just so long as it is shaped conformably tocompletely fill the stepped portion of cylinder 18.

The dielectric member 22 is mounted with its longitudinal axiscoincident with the longitudinal axis of the member 18 and has an upperflat surface 26 and a lower surface 24. The upper surface 26 ofdielectric member 22 lies adjacent to and in contact with the outersurface 30 of insulating member 32 and the outer surface 36 of cylinder18. The lower surface 24 of dielectric member 22 may, if desired, have astepped semi-circular or segmental projection therefrom to vary itsthickness. This projection then provides two lower parallel surfaces 4-2and 44.

The cylindrical electrically conductive member 20 is mounted forsimultaneous rotation with the dielectric member 22 and has its uppersurface 34 in conformably mating contact with tne lower surface 24 ofdielectric member 22. The longitudinal axis of cylinder 20 is coincidentwith the longitudinal axis of dielectric member 22.

The cylinder 2i) may, if desired, have a stepped segmental orsemi-circular portion projecting from the upper surface 34 to form twoparallel surfaces 46 and 48. These surfaces 46 and 48 are disposed tolie adjacent to and in mating contact with the lower parallel surfaces42 and 44 respectively, of dielectric member 22.

Since most of the capacity of the condenser is produced by that portionof the metal cylinder 18 which is in contact with the dielectric member22 and by the surface area of the metal cylinder 2% in contact withdielectric member 22 and directly opposite the contacting portion ofcylinder 18, and since the capacity of a condenser varies inversely withthe distance between its plates, the capacity of the condenser describedherein is less when cylinder 18 and insulating block 32, rotatable withcylinder 18, are rotated out of registry from the position shown inFIGURE 2 to the position shown in FIGURE 3. The capacity of thecondenser can therefore be continuously varied during the rotation ofcylinder 18 and insulating block 32 between the maximum and minimumextreme positions indicated in FIGURES 2 and 3 respectively. The ratioof maximum to minimum capacity can be controlled by varying thethickness of the dielectric member 22; therefore, to change thecapacitance of the condenser 12, the thickness of the dielectric member22 must be decreased or increased accordingly.

Cylinder 18 and insulating member 32 can be rotated together by anyconvenient means. The screw means 17, shown in the drawing, is typicalof many other means that can be used. Screw 17 is secured to cylinder18. To rotate cylinder 18 and member 32 to a second position it is onlynecessary to rotate screw 17 with a force necessary to overcome thefrictional resistance between cylinder 18, member 32 and housing 14.Because of the snug fit between the housing and interior elements of thecondenser, the cylinder 18 and member 32 will remain in this secondposition until application of a further force which overcomes thefrictional resistance between the inten'or elements of the condenser andthe housing.

The plane where the outer surface 36 of cylinder 18 and the outersurface 30 of insulating member 32 come in contact with the uppersurface 26 of dielectric member 22 defines a plane of relative movement.Thus, while cylinder 18 and member 32 are being rotated by screw 17,cylinder 20 and dielectric member 22 are retained in position by virtueof the snug fit and frictional resistance between housing 14 andcylinder 20 and member 22. If desired, screw 17 may be secured tocylinder 20 for rotation thereof and cylinder 18 and insulating member32 can remain stationary while cylinder 20 and dielectric member 22 arerotated; however, the use of either alternative is encompassed by theinventive concept of the present invention.

Because the elements of the condenser as set forth herein fit snuglytogether and because it is solidly constructed there are no effectiveopenings on the surfaces to be presented to the atmosphere; therefore,all air pockets in the condenser are eliminated even while itscapacitance is being changed and the condenser will exclude any fluidswhich may affect proper operation of the condenser. The condenser of thepresent invention, therefore, is effective in any environment and underany atmospheric conditions.

Although certain specific embodiments have been disclosed and describedit will be readily apparent to those skilled in the art that othermodifications can be made, such as changing the configuration of thecylinders, the dielectric member and the insulating member, it beingonly essential that the parts fit snugly together. Therefore, thisapplication should be taken in an illustrative rather than in a limitingsense with the realization that these modifications may be made withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

I claim:

1. A solid dielectric variable condenser comprising a first electricallyconductive member disposed for rotation about its longitudinal axis andhaving a single stepped portion cut into its outer surface, a segmentalinsulating member mounted for rotation with said first member andconformably shaped to completely fill said stepped portion and have itsouter surface lie flush with the outer surface of said first member, adielectric of varying thickness including upper and lower surfaces anddisposed with its upper surface in contact with the outer surfaces ofsaid first member and said insulating member, a second cylindricalelectrically conductive member including an upper surface disposedadjacent to said lower surface of said dielectric, means for selectivelyrotating said first member and said insulating member relative to saiddielectric and said second member, means for providing electricpotential to said first and second members, means electrically isolatingsaid first and second members and holding said first member and saidinsulating member for rotation relative to said dielectric and saidsecond member.

2. A condenser as set forth in claim 1 wherein said electricallyisolating and holding means is a housing in which said first member,said insulating member, said dielectric and said second member are allaligned along their longitudinal axis.

3. A solid dielectric variable condenser comprising a first cylindricalelectrically conductive member disposed for rotation about itslongitudinal axis and having a single stepped semi-circular portionprojecting therefrom to provide a pair of outer parallel surfacesthereon, a semicircular insulating member mounted for rotation with saidfirst member including outer and inner surfaces and having its innersurface adjacent to and in contact with one of said outer parallelsurfaces of said first member and having its outer surface flush withthe other said outer parallel surface of said first member, acylindrical dielectric of varying thickness including upper and lowersurfaces said upper surface in contact with said outer surfaces of saidfirst member and said insulating member, a second electricallyconducting member including an upper surface disposed adjacent saidlower surface of said dielectric, means supplying an electric potentialto said first and second members, means electrically isolating saidfirst and second members and holding said first member and saidinsulating member for rotation relative to said dielectric member andsaid second member.

4. A solid dielectric variable condenser as set forth in claim 3 whereinsaid cylindrical dielectric has a stepped semi-circular portionprojecting therefrom to form a pair of lower parallel surfaces thereon.

5. The condenser as set forth in claim 4 wherein said second cylindricalelectrically conducting member has a stepped semi-circular portionprojecting therefrom to form a pair of upper parallel surfaces thereon,said upper parallel surfaces in contact with said lower parallelsurfaces of said insulating member.

6. A solid dielectric variable condenser comprising a pair of relativelyrotatable capacitor plates disposed for electrical connection tocorresponding conductors, a dielectric member of varying thicknessdisposed between said plates, an insulating member adjacent said firstplate and mounted for rotation therewith, each of said plates providedwith areas in apposition movable in and out of registry across saiddielectric and said insulating member responsive to the relativerotation of said plates for control of the capacitance.

References Cited in the file of this patent UNITED STATES PATENTS1,553,971 Apostol Sept. 15, 1925 2,748,328 Font May 29, 1956 2,913,644Bleazey Nov. 17, 1959 FOREIGN PATENTS 452,573 Great Britain Aug. 25,1936 764,965 Germany June 8, 1954

6. A SOLID DIELECTRIC VARIABLE CONDENSER COMPRISING A PAIR OF RELATIVELYROTATABLE CAPACITOR PLATES DISPOSED FOR ELECTRICAL CONNECTION TOCORRESPONDING CONDUCTORS, A DIELECTRIC MEMBER OF VARYING THICKNESSDISPOSED BETWEEN SAID PLATES, AN INSULATING MEMBER ADJACENT SAID FIRSTPLATES AND MOUNTED FOR ROTATION THEREWITH, EACH OF SAID PLATES PROVIDEDWITH AREAS IN APPOSITION MOVABLE IN AND OUT OF REGISTRY ACROSS SAIDDIELECTRIC AND SAID INSULATING MEMBER RESPONSIVE TO THE RELATIVEROTATION OF SAID PLATES FOR CONTROL OF THE CAPACITANCE.